The most common solution for driving a fan in a modern cooling tower utilizes a induction motor, a drive shaft, disk couplings associated with the drive shaft, and a right angle gearbox, all interconnected to drive a fan of the cooling tower. A typical arrangement is shown in FIG. 1. Generally speaking, a motor 10 is installed outside a cooling tower 12 and a right angle gearbox 14 is installed in the cooling tower and a drive shaft 16 connects the two together via disk couplings 18 to rotate a fan 20 of the cooling tower. The motor is typically a standard National Electrical Manufactures Association (NEMA) frame induction motor. Depending upon the application, a variable frequency drive 22 may be re used to control the speed of the induction motor 10.
There are several drawbacks with this arrangement. It is often difficult to maintain proper lubrication of the right angle gearbox at low speed. Because of the inertia of the drive chain and fan, the induction motor often draws high levels of current at start-up. The right angle gearbox and drive shaft often have maintenance problems caused by fatigue, vibration, misalignment, contamination, and lack of lubrication. The methods disclosed herein solve these issues with an electrically efficient drive mechanism.